Moveable bumper for a dock leveler

ABSTRACT

A dock leveler system includes a pivotal deck whose movement provides the impetus for moving a bumper between an operative position and a retracted position. The bumper is movable relative to the deck, so that after a truck bumps up against the bumper, the bumper can move below the deck to avoid creating an obstacle to a forklift or the like traveling on the deck. The moveable bumper can be disposed within the width of a dock leveler deck that encompasses the full-width of a truck bed. Of the various embodiments, some bumpers pivot underneath the deck, and others move straight up and down. In the operative position, some bumpers are flush with the top of the deck, and others protrude above the deck.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The subject invention generally pertains to dock leveler systemand more specifically to a bumper that moves in response to movement ofa dock leveler deck.

[0003] 2. Description of Related Art

[0004] Dock levelers are often used to compensate for a heightdifference that may exist between a loading dock platform and the bed ofa truck parked at the dock. A dock leveler system typically includes aramp or deck that is hinged at its back edge to raise or lower itsdistal front edge to generally match the height of the truck bed. Oftenan extension plate or lip is pivotally coupled to the ramp to bridge thegap between the ramp's front edge and a back edge of the truck bed. Theramp and extended lip provide a path for forklift trucks to travel fromthe loading dock platform and onto the truck bed, thus facilitatingloading or unloading the truck.

[0005] When a truck backs into the dock, bumpers mounted adjacent thedock leveler are often used to help prevent the rear of the trailer bedfrom damaging itself or the dock. There are usually two spaced-apartbumpers mounted to the front face of the dock with one on either side ofthe dock leveler. This allows the lip and pivoting deck to operatewithin the span between the two bumpers. To prevent a truck from backingup between the two bumpers and striking the dock leveler, the bumpersare usually spaced apart at something less than the full width of astandard size truck. Thus, for dock levelers that operate between suchbumpers, the widths of the deck and lip need to be significantly lessthan that of a standard truck. Unfortunately, in below-dock operation, arelatively narrow deck may limit a forklift's access to the right andleft rear portion of the truck bed, as explained in U.S. Pat. No.6,070,283.

[0006] However, providing an extra wide deck that extends the full widthof a standard-width truck may place the bumpers too far apart toeffectively engage trucks that are relatively narrow or are off-centerto the bumpers. If the bumpers are installed below the front edge of afull-width deck, the bumpers may prevent the deck from descending belowthe dock platform for “below-dock” operation. Operating below-dock is acommon practice when servicing trucks whose bed is lower than the dockplatform.

[0007] To avoid a bumper/deck interference problem with below-dockoperation, moveable bumpers can be used, such as those disclosed in U.S.Pat. No. 4,420,849 and European Patent 0 040 388. Both references showbumpers that can retract by swinging underneath the deck from theiroperative position to a stored position. However, the movement of thebumpers is provided by what appears to be hydraulic cylinders. Suchcylinders, when dedicated to operating just the bumpers, add substantialcost to a dock leveler system. The cost includes the initial cost plusongoing maintenance of the cylinders, as well as their related valves,hydraulic lines and controls.

[0008] U.S. Pat. No. 5,881,414 shows another example of a bumper whosemovement is provided by a dedicated powered cylinder. However, the deck(item 11) is less than the full width of the dock leveler pit, as deck11 is situated between the independent bumper support beams (item 20).Also, a height differential between deck 11 and beams 20 can create astep along either side edge of deck 11, as shown in the patent's FIG. 4.Such a step could be a tipping hazard for a forklift and may pose otheroperational difficulties.

SUMMARY OF THE INVENTION

[0009] To provide full access to the right and left rear portions of atruck bed, a dock leveler system includes a deck with a moveable bumperthat lies within the width of the deck. The bumper is able to move outof the way to avoid interfering with the operation of the deck and toavoid creating an obstacle to a forklift or the like traveling on thedeck. The deck engages the bumper, so that the movement of the deck iswhat moves the bumper, thereby eliminating the need for a separatelypowered bumper actuator.

[0010] In some embodiments, a pivotal deck moves the bumper in onedirection, while a spring urges the bumper in an opposite direction.

[0011] In some embodiments, the bumper moves linearly.

[0012] In some embodiments, the bumper pivots.

[0013] In some embodiments, the bumper moves from an operative positionfacing the rear of a truck parked at the dock to a retracted positionunderneath the deck.

[0014] In some embodiments, the bumper and deck are coupled to eachother by way of a mechanism that has an active mode and a disabled mode,such that downward movement of the deck forces the bumper down when inthe active mode; however, in the disabled mode the bumper remainssubstantially stationary as the deck descends to a cross-trafficposition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a side view of one embodiment of a dock leveler systemwith its deck in a cross-traffic position and its bumper in an operativeposition.

[0016]FIG. 2 is a top view of the dock leveler system of FIG. 1 with aright-front portion of the deck cut away to show features of a mechanismthat connects to a bumper.

[0017]FIG. 3 is a perspective view of a bumper and a four-bar linkageused in the dock leveler system of FIG. 1, but with the springs of thelinkage removed to more clearly illustrate other features of thelinkage.

[0018]FIG. 4 is the same as FIG. 1, but with the deck raised, lippendant and a mechanism of the dock leveler system in a disabled mode.

[0019]FIG. 5 is the same as FIG. 4, but with a lip extended and the dockleveler system mechanism in an active mode.

[0020]FIG. 6 is the same as FIG. 5, but with the deck lowered and thelip extended to place a mechanism of the dock leveler system in a bumperretraction position.

[0021]FIG. 7 is the same as FIG. 6, but with the deck lowered further tomove the bumper below the deck.

[0022]FIG. 8 is another side view of the dock leveler system of FIG. 1,but with the deck in a partially below-dock position, the bumper in aretracted position, and the lip hanging generally pendant.

[0023]FIG. 9 is a side view of another embodiment of a dock levelersystem with its deck in a cross-traffic position and its bumper in anoperative position.

[0024]FIG. 10 is the same as FIG. 9, but with the deck partially raisedand the lip partially extended.

[0025]FIG. 11 is a cross-sectional view of a bumper taken along line11-11 of FIG. 10.

[0026]FIG. 12 is the same as FIG. 9, but with the deck in a below-dockposition, the bumper in a retracted position, and the lip hanginggenerally pendant.

[0027]FIG. 13 is a top view of the dock leveler system of FIG. 9 with aright-front block of the deck removed to show features of the bumper.

[0028]FIG. 14 is similar to FIG. 1, but of another embodiment.

[0029]FIG. 15 is similar to FIGS. 6 and 7, but of the embodiment of FIG.14.

[0030]FIG. 16 is similar to FIG. 8, but of the embodiment of FIG. 14.

[0031]FIG. 17 is similar to FIG. 1, but of yet another embodiment.

[0032]FIG. 18 is similar to FIGS. 6 and 7, but of the embodiment of FIG.17.

[0033]FIG. 19 is similar to FIG. 8, but with the deck at its maximumbelow dock position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] Referring to FIGS. 1 and 2, in order to compensate for a heightdifference that may exist between a loading dock platform 10 and a truckbed 12, a dock leveler 14 includes a ramp or deck 16 that is hingedalong its rear pivotal edge 18 to raise or lower its front distal edge20 to generally match the height of truck bed 12. Referring to FIG. 2,deck 16 has a length 22 extending between edges 18 and 20, and has awidth 24 extending between a right edge 26 and a left edge 28. A hinge30 pivotally couples an extension plate or lip 32 to deck 16, so thatlip 32 can swing out and rest upon the rear edge of truck bed 12, thusbridging the gap between the deck's front edge 20 and the rear of truckbed 12. Together, deck 16 and extended lip 32 provide a path for aforklift truck and personnel to travel between platform 10 and truck bed12, thus facilitating the loading and unloading of the truck.

[0035] To help protect the rear of the truck or the dock from impactwhen a truck backs into the dock, preferably two bumpers 34 areinstalled along either side of dock leveler lip 32. Each bumper 34 hasan abutment surface 36 that typically protrudes beyond a face 38 of thedock. Bumpers 34 are spaced apart to provide enough room for lip 32 tooperate between the two while being sufficiently close to prevent therear of the truck from contacting the building and/or the dock levelerlip.

[0036] The actual structure used to mount bumpers 34 can vary, butpreferably the mounting structure is such that it enables the pivotalmovement of the deck to provide the impetus that moves bumpers 34between an operative position and a retracted position. In the operativeposition, abutment surface 36 of each bumper 34 is in a position toabsorb or receive an impact 39 from an incoming truck. In the retractedposition, bumpers 34 are beneath the deck structure to provide a clearpath for traffic across the top surface of deck 16, even when deck 16 isin a below-dock position, i.e., front edge 20 is below floor level ofdock platform 10.

[0037] In one embodiment, the structure used in mounting and operatingbumpers 34 includes a mechanism 40 that comprises a four-bar linkage 42plus an operator 44, as shown in FIGS. 1-3. However, it should be notedthat mechanism 40 is just one example of a mechanism that allows themovement of deck 16 to reposition bumper 34 between an operativeposition and a retracted position. Other mechanism for performing thegeneral function of mechanism 40 would include, but not be limited tomechanisms employing cables, ropes, chains, gears, sprockets, pulleys,etc. Nonetheless, for some embodiments, operator 44 is pivotallyconnected to deck 16 by way of a pin 46, while four-bar linkage 42 maybe attached to a frame 48 of dock leveler 14 and/or pit floor 62. Thefour bars of linkage 42 comprise a first link 50, a second link 52, abase 54, and a bumper support arm 56 to which bumper 34 is attached.Each bumper 34 is preferably associated with its own mechanism 40. Thefunction of each mechanism 40 is best understood with reference to theoverall operation of dock leveler system 14 and will be explained withreference to just one side of leveler 14, i.e., one bumper 34 and itsassociated mechanism 40, as both mechanisms 40 operate in the samemanner.

[0038] The operation begins with deck 16 in a cross-traffic position(i.e., the top of deck 16 is generally flush with the floor of platform10), as shown in FIG. 1. The term, “deck” encompasses an upper trafficsurface or a top plate 58 and any related support or supplementalstructure such as those items known as support beams, girders,stringers, end plates, side plates, braces, gussets, tabs, lugs, etc. Arear hinge 60 pivotally couples deck 16 to frame 48, which is installedwithin a dock leveler pit 62. In FIG. 1, lip 32 is shown in its pendantposition with preferably two lip keepers 64 supporting a tip 66 of lip32. Although various well-known, conventional lip designs can be used,in this embodiment lip 32 is mounted for limited sliding motion relativeto a lip support plate 32′, which in turn is pivotally connected to deck16 by way of hinge 30. The sliding connection allows one edge 68 of lip32 to protrude above deck 16 to provide a barricade that helps prevent aforklift from accidentally rolling off the edge of deck 10 when a truckis not present while dock leveler 14 is in its stored position. Furtherdetails of one embodiment of lip 32 are disclosed in U.S. Pat. No.4,920,598, which is specifically incorporated by reference herein. Atthe initial stage of operation, four-bar linkage 42 places itscorresponding bumper 34 in its operative position, as shown in FIGS.1-3. To withstand the impact of a truck backing up against the face 36of bumper 34, much of the impact can be transmitted to deck 16, frame 48and the surrounding concrete of pit 62 by providing bumper 34 with anengagement surface 70 that is adapted to engage deck 16.

[0039] After the truck bumps up against bumper 34 and stops at thedesired position, bumper 34 can be moved out of the way so as not tointerfere with the loading or unloading of the truck. Before movingbumper 34, an actuator, e.g., a hydraulic cylinder 72, first lifts deck16 to raise tip 66 of lip 32 above truck bed 12, as shown in FIG. 4.This disengages surface 70 from deck 16 and allows lip 32 to be extendedout and over truck bed 12 without striking the rear of bed 12, as shownin FIG. 5. The lip actuator for extending lip 32 is not shown, as doingso would detract from other illustrated features of mechanism 40.However, the lip actuator could be any one of those widely used today,such as a conventional hydraulic cylinder.

[0040] With deck 16 raised and lip 32 extended, operator 44 is able toswing forward, as lip 32 disengages an extension 96 that protrudes fromoperator 44. This places mechanism 40 in an active mode, whereindownward movement of deck 16 moves bumper 34 to its retracted position.It should be appreciated by those skilled in the art that instead ofextension 96 protruding from operator 44 another member equivalent infunction to extension 96 could extend from underneath lip 32 and engageoperator 44 as lip 32 pivots downward. However, extension 96 protrudingfrom operator 44 is the currently preferred embodiment.

[0041] To move bumper 34 to its retracted position (where it remainsbelow the upper surface of the deck), deck 16 first descends from itsposition of FIG. 5 to that of FIG. 6. This engages an edge 76 ofoperator 44 with a protrusion 78 of four-bar linkage 42. A lug 80rigidly extending from bumper support arm 56 fixes protrusion 78relative to bumper 34, so moving protrusion 78 moves bumper 34. From theposition of FIG. 6, further downward movement of deck 16 lowers lip 32upon truck bed 12 to facilitate the loading and/or unloading of thetruck, as shown in FIG. 7. However, the downward deck movement alsoprovides the impetus that causes operator 44 to push against protrusion78, which in turn pivots bumper support arm 56 about a pin 82 thatpivotally couples arm 56 to base 54. At the same time, a pin 84 providesrelative rotation between first link 50 and arm 56, a pin 86 providesrelative rotation between second link 52 and base 54, and a pin 88provides relative rotation between links 50 and 52

[0042] The relative movement of arm 56, base 54, and links 50 and 52creates unlimited opportunities to provide four-bar linkage 42 with aspring-return action. The spring-return can be provided by springs ofalmost any style including, but not limited to, a tension spring,compression spring, torsion spring, and gas spring. Other mechanisms forreturning bumper 34 to its operative position are also well within thescope of the invention. For the embodiment of FIGS. 1-8, one or moretensions springs 90 connect pins 82 and 88 to urge bumper 34 to itsoperative position. For clarity, springs 90 are not shown in FIG. 3;however, in some installations, two tension springs 90 connect pin 82 topin 88 with one spring 90 on each protruding end of pin 88, as shown inFIG. 2. In other embodiments, a single spring provides tension betweenpins 82 and 88.

[0043] After completing the loading or unloading of cargo from truck bed12, dock leveler 14 is commonly returned to its stored or cross-trafficposition of FIG. 1. To return leveler 14 and bumpers 34 to theiroriginal positions of FIG. 1 without having to first raise deck 16 allthe way back up to its position of FIG. 4, edge 76 of operator 44 isfirst disengaged from protrusion 78. To do this, deck 16 and lip 32 areallowed to descend to the below-dock position shown in FIG. 8. Upon deck16 lowering to this predetermined position (or even lower, as shown inFIG. 19), a tip 92 (or some other portion of operator 44) engages arelease surface, such as plate 94, base 54, frame 48, pit 62 or someother structure associated with the system of leveler 14. This forcesedge 76 to disengage protrusion 78 by plate 94 effectively rotatingoperator 44 counterclockwise (as viewed in FIG. 8) about pin 46. Withedge 76 disengaged from protrusion 78, deck 16 only needs to rise justhigh enough for bumper 34 to spring back out from underneath deck 16.Once bumper 34 returns to its operative position, deck 16 can lower onceagain to its stored, cross-traffic position of FIG. 1.

[0044] It should be appreciated by those skilled in the art that levelersystem 14 in the position of FIG. 19 can also be useful in certainbelow-dock situations. For example, it may be desirable to add or removea load at the very rear of truck bed 12 without using lip 32. Otherwise,if lip 32 were fully extended and resting on truck bed 12, lip 32 mightbe resting at the very location where the load needs to be added orremoved.

[0045] To prevent bumper 34 from moving to its retracted position whileattempting to lower deck 16 from its raised position of FIG. 4 to itsstored position of FIG. 1, operator 44 can be provided with an extension96 that lip 32 or its plate 32′ can selectively engage. When lip 32 isgenerally pendant, as shown in FIG. 4, lip 32 pushes against extension96 to tilt operator 44, so that edge 76 clears protrusion 78 when deck16 descends. However, when lip 32 extends, as shown in FIG. 5, lip 32disengages extension 96 to allow operator 44 to swing its edge 76 intoalignment with protrusion 78 as deck 16 descends. Thus, lip 32disengaging extension 96 places mechanism 40 in an active mode, whereindownward movement of deck 16 can move bumper 34 to its retractedposition. Alternately, lip 32 engaging extension 96 places mechanism 40in a disabled mode, which permits downward movement of deck 16 whilebumper 34 remains at its operative position.

[0046] In another embodiment, shown in FIGS. 9-13, a dock leveler system98 uses pivotal movement of a deck 100 to move a bumper 102 generallylinearly between an operative position (FIGS. 9 and 10) and a retractedposition (FIG. 12). Although leveler 98 preferably includes two bumpers,the structure and function of the bumpers will be described withreference to just one, as both bumpers are identical or very similar.

[0047] To render bumper 102 moveable between its operative and retractedpositions, bumper 102 is mounted for vertical movement to a track 104that is attached to face 38 of the dock. To urge bumper 102 upward toits operative position, a bar 106 extends from an upper end of track104, and another bar 108 extends from a lower end of bumper 102 with atension spring 110 connecting the two bars 106 and 108. However, insteadof spring 110, it is well within the scope of the invention to movebumper 102 upward using another device, such a compression spring, gasspring, counter weight, etc. A stop 112 on bumper 102 engages bar 106 tolimit the upward travel of bumper 102.

[0048] To allow the downward movement of deck 100 to lower bumper 102 toits retracted position, deck 100 includes an angled block 114 that moveswith the rest of deck 100 and can selectively engage an engagementsurface 116 of bumper 102. In a preferred embodiment, block 114 includesan upper lip 118 that overlays surface 116 of bumper 102. Thus, as deck100 pivots downward, lip 118 pushes against surface 116 to move bumper102 from its operative position of FIG. 9 to its retracted position ofFIG. 12.

[0049] Spring 110 returns bumper 102 to its operative position when deck100 pivots upward from its below-dock position of FIG. 12 to itscross-traffic position of FIG. 9.

[0050] Since stop 112 limits the upward movement of bumper 102, block114 separates from bumper 102 when cylinder 72 lifts deck 100 furtherfrom its cross-traffic position of FIG. 9 to a raised position of FIG.10.

[0051] So that bumper 102 can withstand an impact from a truck thatbacks up against it, bumper 102 gains horizontal structural support fromdeck 100, which is much sturdier than bumper 102 and track 104. This isachieved by placing an angled face 120 of block 114 adjacent to asimilarly angled face 122 on bumper 102. The two faces 120 and 122 areadjacent when deck 100 is in its cross-traffic position of FIG. 9. Thus,a horizontal impact from a truck is transmitted through bumper 102,block 114, deck 100, and onto frame 48 and the surrounding concrete ofthe dock. Although the two faces 120 and 122 are angled to allow deck100 to pivot without the two faces 120 and 122 binding against eachother, the angle is preferably at a minimum to avoid raising the deckdue to the impact of the truck. Also, when deck 100 is in itscross-traffic position of FIG. 9, the two faces 120 and 122 arepreferably about 0.13 inches apart to ensure that spring 110 can raisebumper 102 without excessive frictional resistance between the two faces120 and 122. However, the spacing between the two faces 120 and 122should preferably not be so great that bumper 102 or track 104 wouldneed to yield plastically before making contact between the two faces.The actual use of dock leveler 98 is similar to that of dock leveler 14with regards to loading and unloading a truck, operating the deck, andoperating lip 32; however, operator 44, extension 96 and plate 94 arenot required.

[0052] In another embodiment, similar to dock leveler system 14 andshown in FIGS. 14-16, a dock leveler 130 includes a bumper 34′ thatprotrudes above deck 16′ to help prevent truck beds from overriding deck16″ (i.e., the bottom of the truck bed being higher than deck 16′). Atruck bed overriding a dock leveler deck can occur in applications wherea low dock height designed for low trailer beds has to also receivetrailers of standard bed height. To ensure that bumper 34′ does notcreate an obstruction to material handling equipment traveling on deck16′, leveler system 130 includes a mechanism 40′ that allows bumper 34′to tuck underneath deck 16′.

[0053] To enable the movement of deck 16′ to move bumper 3′ from itsoperative position of FIG. 14 to its retracted position of FIG. 16,mechanism 40′ includes a four-bar linkage 42′ and an operator 44′, whichfunction in a manner similar to that of four-bar linkage 42 and operator44. More specifically, after the truck has backed against bumper 34′,deck 16′ is raised and the dock leveler lip is extended to allow a notch76′ in operator 44′ to engage a protrusion 78′ that is attached tobumper 34′ by way of a lug plate 80′. Operator 44′ includes an extensionsimilar in function and structure to that of extension 96 of FIG. 1.However, the extension is not shown in FIGS. 14-16 to avoid clutteringthe drawing figures with details that are already shown and readilyunderstood with reference to the drawing figures of dock leveler system14. With notch 76′ of operator 44′ engaging protrusion 78′, subsequentdownward movement of deck 16′ forces four-bar linkage 42′ to collapsefrom its configuration of FIG. 15 to that of FIG. 16. In doing so,bumper 34′ pivots about pin 82″ to its retracted position of FIG. 16,and a tension spring 90′ (which extends between pins 132 and 88′)stretches, which urges bumper 34′ back toward its operative position ina manner similar to that of spring 90 of dock leveler 14. A plate 94′(similar to plate 94) forces operator 44′ to disengage from protrusion78′. Returning leveler 130 from it bumper-retracted position of FIG. 16to its bumper-operative position of FIG. 14 can be done by first raisingand then lowering deck 16′, in a manner similar to that described ofleveler system 14.

[0054] Bumper 34′ could be modified to protrude even further above deck16′ than what is shown in FIG. 14 and still have sufficient clearance totuck underneath deck 16′ by simply increasing the effective length ofoperator 44′ (i.e., increasing the distance between notch 76′ and a pin46′). The actual structure of bumper 34′ and mechanism 40′ can vary;however, in a preferred embodiment, bumper 34′ is made of square steeltubing that is reinforced with an internal gusset and beveled and cappedat each end. To provide bumper 34′ with a positive stop at its operativeposition, as shown in FIG. 14, a lower edge 134 of bumper 34′ abuts afixed end plate 136 on a base 54′ of four-bar linkage 42′.

[0055] In yet another embodiment, shown in FIGS. 17 and 18, a dockleveler system 138 includes a mechanism 140 that can replace four-barlinkage 42 of dock leveler 14 or replace four-bar linkage 42′ of leveler130. With regards to structure and function, an operator 44″, extension96″ a protrusion 78″, a bumper 34″, a base 54″, and a plate 94″ of dockleveler 138 are closely related respectively to operator 44, extension96, protrusion 78, bumper 34, base 54 and plate 94 of dock lever 14.However, instead of tension spring 90, mechanism 140 includes acompression spring 142 that urges bumper 34″ to its operative positionof FIG. 17. To accomplish the spring return of bumper 34″, a guide rod144 runs through the center of spring 142 and extends between a pin 82″in base 54″ and a lug 80″ (which connects protrusion 78″ to bumper 34″).A block 148 slides on rod 144, and a link 150 is pivotally connected toa pin 146 on base 54″ and a pin on block 148. In operation, deck 16″descending from its position of FIG. 18 forces operator 44″ to pushagainst protrusion 78″, which pivots bumper 34″ downward about pin 82″.As bumper 44″ pivots, link 150 forcibly slides block 148 along rod 144to compress spring 142, which facilitates the return of bumper 34″ toits operative position.

[0056] Although the invention is described with reference to a preferredembodiment, it should be appreciated by those skilled in the art thatvarious modifications are well within the scope of the invention. Forexample, the lip extension in any of the embodiments could move linearlybetween extended and stored positions, as opposed to pivoting betweenextended and pendant positions. Although the use of two bumpers per dockleveler system is preferred, it is possible to use just one. The bumperscan be made of a variety of materials including, but not limited tosteels, polymers, and various combinations thereof. Moreover, thebumpers can be shock absorbing, or they can be relatively solid andunyielding, whereby, in the later case, the dock leveler is structuredto absorb the impact of the truck. Therefore, the scope of the inventionis to be determined by reference to the claims that follow.

We claim:
 1. A bumper assembly for a dock leveler system having a deckthat can pivot, comprising: a bumper moveable between an operativeposition and a retracted position under an impetus of deck movement,wherein the bumper is moveable relative to the deck.
 2. The bumperassembly of claim 1, further comprising an engagement surface carried bythe bumper and being adapted to selectively engage and disengage thedeck upon the bumper moving between the operative position and theretracted position.
 3. The bumper assembly of claim 1, furthercomprising a spring coupled to the bumper to urge the bumper to theoperative position.
 4. The bumper assembly of claim 3, wherein thespring is a tension spring.
 5. The bumper assembly of claim 3, whereinthe spring is a compression spring.
 6. The bumper assembly of claim 1,wherein the bumper pivots between the operative position and theretracted position.
 7. The bumper assembly of claim 1, wherein thebumper moves substantially linearly between the operative position andthe retracted position.
 8. The bumper assembly of claim 1, wherein thebumper is moveable downward from the operative position to the retractedposition in reaction to the deck pivoting downward.
 9. The bumperassembly of claim 1, wherein the bumper is moveable upward from theretracted position to the operative position in reaction to the deckpivoting upward.
 10. The bumper assembly of claim 1 further comprising amechanism coupleable to the deck and the bumper and having an activemode and a disabled mode, wherein the mechanism in the active modeallows downward movement of the deck to move the bumper to the retractedposition, and wherein the mechanism in the disabled mode allows downwardmovement of the deck while the bumper remains substantially at theoperative position, whereby the disabled mode allows the deck to descendto a cross-traffic position while the bumper remains at the operativeposition.
 11. The bumper assembly of claim 10, wherein the dock levelersystem includes a lip plate pivotally coupled to the deck, and whereinthe mechanism is engageable by the lip so that movement of the lippositions the mechanism between the active mode and the disabled mode.12. The bumper assembly of claim 11, further comprising a releasesurface located to be engaged by the mechanism upon the deck descendingto a predetermined below-dock position, wherein the mechanism engagingthe release surface repositions the mechanism from the active mode tothe disabled mode.
 13. The bumper assembly of claim 1, wherein thebumper in the operative position is adapted to protrude above the deck,and wherein the bumper in the retracted position is adapted to be belowthe deck.
 14. A bumper assembly for a dock leveler system having a deckthat can pivot, comprising: a spring adapted to provide a spring force;and a bumper coupled to the spring and being moveable to a retractedposition under an impetus of deck movement, and urged to an operativeposition under an impetus of the spring force.
 15. The bumper assemblyof claim 14, further comprising an engagement surface carried by thebumper and being adapted to selectively engage the deck when the bumperis in the operative position and disengage the deck when the bumper isin the retracted position.
 16. The bumper assembly of claim 14, whereinthe bumper is moveable downward from the operative position to theretracted position in reaction to the deck pivoting downward.
 17. Thebumper assembly of claim 14, wherein the bumper is moveable upward fromthe retracted position to the operative position in reaction to the deckpivoting upward.
 18. The bumper assembly of claim 14, wherein the bumperpivots between the operative position and the retracted position. 19.The bumper assembly of claim 14, wherein the bumper moves substantiallylinearly between the operative position and the retracted position. 20.The bumper assembly of claim 14, wherein the spring is a tension spring.21. The bumper assembly of claim 14, wherein the spring is a compressionspring.
 22. The bumper assembly of claim 14, further comprising amechanism coupleable to the deck and the bumper and having an activemode and a disabled mode, wherein the mechanism in the active modeallows downward movement of the deck to move the bumper to the retractedposition, and wherein the mechanism in the disabled mode allows downwardmovement of the deck while the bumper remains substantially at theoperative position, whereby the disabled mode allows the deck to descendto a cross-traffic position while the bumper remains at the operativeposition.
 23. The bumper assembly of claim 22, wherein the dock levelersystem includes a lip plate pivotally coupled to the deck, and whereinthe mechanism is engageable by the lip so that movement of the lippositions the mechanism between the active mode and the disabled mode.24. The bumper assembly of claim 23, further comprising a releasesurface located to be engaged by the mechanism upon the deck descendingto a predetermined below-dock position, wherein the mechanism engagingthe release surface repositions the mechanism from the active mode tothe disabled mode.
 25. The bumper assembly of claim 14, wherein thebumper in the operative position is adapted to protrude above the deck,and wherein the bumper in the retracted position is adapted to be belowthe deck.
 26. A bumper assembly for a dock leveler system having a deckthat can pivot, comprising: a bumper moveable between an operativeposition and a retracted position under an impetus of deck movement; andan engagement surface carried by the bumper and being adapted toselectively engage and disengage the deck upon the bumper moving betweenthe operative position and the retracted position.
 27. The bumperassembly of claim 26, further comprising a spring coupled to the bumperto urge the bumper to the operative position.
 28. The bumper assembly ofclaim 26, wherein the bumper is moveable downward from the operativeposition to the retracted position in reaction to the deck pivotingdownward.
 29. The bumper assembly of claim 26, wherein the bumper ismoveable upward from the retracted position to the operative position inreaction to the deck pivoting upward.
 30. The bumper assembly of claim26, further comprising a mechanism coupleable to the deck and the bumperand having an active mode and a disabled mode, wherein the mechanism inthe active mode allows downward movement of the deck to move the bumperto the retracted position, and wherein the mechanism in the disabledmode allows downward movement of the deck while the bumper remainssubstantially at the operative position, whereby the disabled modeallows the deck to descend to a cross-traffic position while the bumperremains at the operative position.
 31. The bumper assembly of claim 30,wherein the dock leveler system includes a lip plate pivotally coupledto the deck, and wherein the mechanism is engageable by the lip so thatmovement of the lip positions the mechanism between the active mode andthe disabled mode.
 32. The bumper assembly of claim 31, furthercomprising a release surface located to be engaged by the mechanism uponthe deck descending to a predetermined below-dock position, wherein themechanism engaging the release surface repositions the mechanism fromthe active mode to the disabled mode.
 33. The bumper assembly of claim26, wherein the bumper in the operative position is adapted to protrudeabove the deck, and wherein the bumper in the retracted position isadapted to be below the deck.